Retention paper

Unexpectedly low values of first-pass retention can result from a variety of system changes.

Retention aid chemical name

For instance, an overdose of retention aid is likely to produce a highly flocced sheet that is unacceptable to the customer. If the paper has a higher than necessary degree of fiber flocculation, then it may be a good idea to cut back on the retention aid dosage. Function: To maintain adequate efficiency, drainage, and cleanliness of a paper machine; to achieve adequate Z-directional uniformity; to retain additives, including fillers. Successful operation of an online retention control system can yield substantial benefits. Isogai, A. The greater part of the white water is returned to the stock, with the result that the concentration of fines and fillers gradually increases. Since the surface area of fillers tends to be much higher than the same mass of cellulosic material, the effect may be equivalent to a reduction in the amount of retention aid being added. The same effect can happen due to other changes that increase the specific surface area of the furnish, i. Furthermore, most modern paper machine systems are well equipped with save-alls , so relatively few fiber fines may leave with the wastewater, even if the retention efficiency in the forming section is very poor.

Does it get worse only when the paper grade is changed to a lower basis weight? In addition to neutralizing some of the excess anionic charge of the solid surfaces in the furnish, such additives tend to form positively charged " patches " that can be attracted to negatively charged areas on other solid surfaces in the furnish.

There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives.

first pass retention paper

Isogai, A. An additional layer of online control can be beneficial if there are large variations in the cationic demand. Moderate use of retention aids tends to keep the paper machine system cleaner by lowering the amounts of fines and pitch -like particles or emulsion droplets that are floating freely in the process water.

Retention agent salary

Additional strategies are mentioned under the headings for several of the additives that are often used in retention aid programs. The greater part of the white water is returned to the stock, with the result that the concentration of fines and fillers gradually increases. A moderate level of retention aid treatment helps keep such fine material bound to the fibers, eliminating some of the potential for short-term swings in basis weight. In addition to keeping the retention level almost constant, it can be expected that the basis weight and paper properties also will remain within tighter limits. Rather, your customers will focus on attributes such as brightness , strength , dust , wrinkles, and wavy edges - attributes that affect the end-use of the product. Furthermore, most modern paper machine systems are well equipped with save-alls , so relatively few fiber fines may leave with the wastewater, even if the retention efficiency in the forming section is very poor. Posted on November 14, by admin Retention Aid is the key to cost savings in paper mill. The anionic colloids can include such substances as wood pitch , carry-over of black liquor in the case of unbleached kraft paper production, carry-over of oxidized hemicellulose byproducts in the case of bleached kraft paper production, dispersants present in coated broke, anionic direct dyes in the case of deep color paper production, and dispersants in certain slimacides. References Aloi, F. It should be retention otherwise face to following troubles: Fine fiber particles and filler drainage Higher additives and sizing cost Increased deposits. Moderate use of retention aids tends to keep the paper machine system cleaner by lowering the amounts of fines and pitch -like particles or emulsion droplets that are floating freely in the process water. Since the surface area of fillers tends to be much higher than the same mass of cellulosic material, the effect may be equivalent to a reduction in the amount of retention aid being added. Finally, one can consider the use of microparticulate additives, which are typically added last to the system, downstream of the retention aid addition point, and usually right after the furnish has passed through a set of pressure screens to redisperse the fibers.

Devices are available from several suppliers for continuous measurement of white water consistency, usually based on optical principles. Retention LowVariableHigh Before taking action to increase the retention efficiency of fine particles during the formation of paper, it is worth taking some time to consider the relative importance of this issue.

You also can review some of the factors mentioned in the previous paragraphs when considering what might be responsible for observed changes in retention.

Retention aid definition

Devices are available from several suppliers for continuous measurement of white water consistency, usually based on optical principles. Since the surface area of fillers tends to be much higher than the same mass of cellulosic material, the effect may be equivalent to a reduction in the amount of retention aid being added. Evidence suggests that the microparticles function by interacting with the very-high-mass retention aid molecules or cationic starch molecules, causing the large molecules to contract. However, it is worth noting that many additional or alternative materials also can be used. But there are some key advantages of maintaining moderately good to excellent retention efficiency. Please send corrections if you find errors or points that need better clarification. For instance, it is possible that the particle size of the mineral filler has decreased, so the total surface area that is available to take up retention aid molecules has increased. There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives. Perhaps the most critical cases are those in which a reactive additive, such as ASA size , has been added to the furnish. A moderate level of retention aid treatment helps keep such fine material bound to the fibers, eliminating some of the potential for short-term swings in basis weight.

Relatively high retention is desirable, however, when using ASA size or when using rosin emulsion size under neutral or alkaline pH, since those additives will tend to gradually decompose if they are not retained in the first pass. Sometimes retention aid efficiency is hurt by the presence of interfering substances.

paper sizing recipe
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Retention and Drainage Aids